The invention relates to a cusped-field thruster for a space system and to a method for generating a thrust on a space system.
Electric thrusters have been under development for several decades by various companies and universities, for example for use in a space system.
Plasma accelerator configurations are described, for example, in DE 101 30 464 A 1 and in DE 103 00 776 B3.
Another plasma accelerator configuration is described, for example, in DE 101 53 723 A 1, wherein for the plasma accelerator configuration a multistage construction is disclosed with at least one intermediate electrode between electrodes enclosing a plasma chamber between them. Due to this so-called “high efficiency multistage plasma thruster” (HEMPT), increased efficiency is achieved by an uneven potential distribution to the potential stages formed by the plurality of electrodes with a high potential difference of the last stage on exit of the plasma jet and by a special design of a magnetic field permeating the plasma chamber in this last stage.
In U.S. Pat. No. 6,448,721 B2, an arrangement and a method for a plasma thruster are described that utilize a so-called Hall thruster with a cylindrical geometry. It is portrayed that this arrangement is suitable for operation with low energy. Efficient operation is accomplished in this case by magnetic fields with a generally radial component.
Other prior art is found, for example, in CN 105736272 A; in Courtney et al., “Diverging Cusped-Field Hall Thruster (DCHT),” IEPC-2007-39; in Matlock et al., “Controlling Plume Divergence in a Cusped-Field Thruster,” IEPC-2011-178; and in Matyash et al., “Comparison of SPT and HEMP thruster concepts from kinetic simulations,” IEPC-2009-159.
FIG. 1 (from Matyash et al., “Comparison of SPT and HEMP thruster concepts from kinetic simulations,” IEPC-2009-159) shows schematically a system of a cusped-field thruster 100 according to the prior art.
The cusped-field thruster 100 consists in this case of a plurality of magnets, the magnetic south poles and magnetic north poles of which are arranged respectively in an antipolar manner A cathode 102 emits electrons for the discharge ignition, wherein the electrons further neutralize the xenon ion beam.
Xenon gas is admitted to the discharge chamber of the cusped-field thruster 100. In this example, a voltage between 300 V and 2000 V is then applied between the cathode 102 and the anode 104.
The xenon particles are ionized and then accelerated through the electric field. After the passage through the neutralizer (cathode 102), which supplies electrons to the ion beam again and thus renders it electrically neutral again, the neutralized particles are ejected in the form of a beam (see right-hand part of FIG. 1).
The cathode 102 as neutralizer here prevents charged particles from moving back to the space system in an arc.
As is to be seen in FIG. 1, the ionized xenon gas is accelerated through the magnetic field, which forms so-called cusps in this case, along the symmetry axis of the thruster.
FIG. 2 shows schematically another system of a cusped-field thruster 200 according to the prior art.
As in the cusped-field thruster shown in FIG. 1, in the cusped-field thruster 200 ionized xenon particles are accelerated along the axis of symmetry through the electric field, which is formed between the cathode 202 and the anode 204.
In contrast to the cusped-field thruster in FIG. 1, the magnetic field lines that are generated by the magnets 206 run parallel to the symmetry axis of the thruster in the region in front of the anode 204.